Flashcards in Global Systems, Earth And Universe Deck (43):
How are stars formed
Red giant/ red supergiant
Planetary nebula/ supernova
White dwarf/ black hole
What is the Hertsprung-Russell Diagram
• By combining absolute magnitude with our understanding of colour and temperature(called spectral class), astronomers can classify all stars on a graph called a Hertsprung-Russell Diagram.
This enables them to classify the type of star they are looking at and helps them to determine many of its characteristics like how old it is, its surface temperature and the stage of its life cycle.
What is the absolute magnitude scale
On the scale of absolute magnitude, objects that are
brighter have a lower absolute magnitude.
• The brightest stars in the night sky have absolute magnitudes generally between -1 to +1.
• The dimmest objects you can just see with your naked eye at night after adjusting to the dark rate at about 6.
• A full moon on a clear night rates at -13.
Why is this important?
Scientists use absolute magnitude to help understand where a star is in its lifecycle because they have determined the absolute magnitudes for each of the different stages. It can also help them determine its mass!
What is the difference between absolute and apparent magnitude
Apparent magnitude is how bright a star appears to us. Clearly our sun has the highest level of apparent magnitude!
Absolute magnitude is the true and actual brightness of a star. It is the true measure of how bright any star would be if it was moved to be exactly 200 parsecs from earth. This means different stars can be compared fairly regardless of how far away they are.
outline of sunspots
Solar astronomers use sunspots to indicate how active the surface of the sun is.
They look darker because they are cooler than surrounding areas but are still extremely hot.
More spots corresponds to higher activity.
Earth’s magnetosphere interacts with mass ejections from the sun producing the auroras – aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere.
Mass ejections from the sun can also interfere with radio waves used in modern telecommunications.
What does hydrogen create different elements
Joins and fuses with its same element to create others
How was our sun formed
• Our sun was formed from a gravitational collapse of
enormous masses of dust and gas.
• This collapse causes enormous levels of heat and pressure eventually triggering nuclear fusion.
• Nuclear fusion is when hydrogen is transformed into helium releasing vast amounts of energy.
• The sun has been doing this for about 5 billion years.
What is parallax
Parallax is a difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle of inclination between those two lines.
Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.
Astronomers can use the principle of stellar-parallax to measure distances to nearby celestial objects by viewing them from the earth at different times because the earth keeps moving.
large objects that orbit stars. Do not produce their own light. Hard to detect.
• Stars = massive, luminous spheres of plasma held together by gravity. Also known as suns. Easy to detect.
enormous collections of stars, planets, gases and dust that are bound by gravity. Usually orbiting a black hole
clouds of dust and gas that may collapse and heat up due to gravity forming stars and planets.
Define the universe
all existing matter, energy, space and time considered as a whole extending to the cosmic horizon.
What is earths position in space
• Our solar system is located on the Outer Orion arm of a spiral galaxy known as the Milky Way galaxy
• The Milky Way is just one of about 130 billion galaxies so far discovered in the known universe
• There are over 250 billion suns (stars) in our galaxy alone.
• The Milky Way Galaxy is about 100,000 light years in diameter but only about 1000 light years thick (Source NASA). It is thus disc like (like a big dinner plate!).
• The magnetic field of the Earth deflects most of the charged particles emanating from the Sun (called solar winds). These particles would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays.
• The origin of the Earth's magnetic field is not completely understood, but is thought to be caused by electrical currents produced by rotation in the earth’s liquid-metallic outer core of iron and nickel.
• This mechanism is termed the
dynamo effect. Why?
Some rocks that harden from the molten state contain indicators of the magnetic field at the time of their solidification.
The study of such "magnetic fossils" indicates that the Earth's magnetic field reverses itself every million years or so (the north and south magnetic poles switch).
Planets with protective magnetic fields are quite rare. This protective magnetic field was of critical importance for the origin of life on earth. Without it, life probably could not start.
The formation of the moon
• The Moon is thought to have formed nearly 4.5 billion years ago, not long after the Earth.
• Although there have been several hypotheses for its origin in the past, the current most widely accepted explanation is that the Moon formed from the pulverised and vaporised debris left over after a giant impact between the Earth and a large asteroid about the size of Mars, called Theia.
• The dust and debris eventually coalesced due to gravity into a sphere but it was too far away to be pulled back to earth.
• This collision most likely also contributed to the Earth’s current rate of spin.
• There remains some argument against this explanation.
More evidence is needed to be certain
Key facts about earth
Of the 9 major planets in our solar system, Earth is 3rd from the sun, the most dense and the fifth largest. (There are now several other dwarf planets recognised as well as Pluto not included in the main 9)
• The Earth has a radius of about 6400 km (circumference about 40,000 km)
• Outer core of molten iron and nickel (liquid) surrounding a solid inner core
made from same metals).
• It formed about 4.6 billion years ago.
• Orbits our sun at an average distance of 150 million km (elliptical orbit)
• Takes one year to orbit sun (940 million km round trip)
• Rotates on its own axis (tilted at 23.5 degrees) once every 24 hours (we are
all moving eastwards at about 1660 km/h!)
• Has a moon most likely made from debris from a collision with the earth colliding with a huge object called Theia about 4.5billion years ago
• Extremely thin layer of protective atmosphere
Protective magnetic field due its molten core and rotation
Only known planet so far to support life
The waters of the earth
Soils and rocks
The oxygens and air
The living things
What are four features that effect our climate
There are four major factors that influence our climate:
1. The amount of energy from the sun reaching the surface
2. The differing abilities of land and water to absorb and emit radiant heat
3. The tilt of the Earth's axis
4. The features of the land
The suns heat reaching the surface
The equatorial region receives more radiation per km2, than any other area on Earth.
• The polar regions receives the least radiation per km2, on Earth.
What is insolation
Insolation is the total amount
of solar radiation energy received on a given surface area of the Earth during a given time
What is radiant flux density
Radiant Flux Density (IOh) is the amount of energy that hits a particular part of the Earth’s outer atmosphere.
• Because the average amount of sun’s radiation (ISC) does not always come in perpendicular to outer atmosphere, the Radiant Flux Density can be worked out using The Cosine Effect:
What is the difference between land and water absorbing heat
During daylight hours the land absorbs radiant heat from the sun more quickly than does water.
• At night heat is radiated from the land more quickly than from the water.
• As a result, the ocean temperature changes less on a daily basis than air and land temperatures.
• This difference creates wind too!
What is specific heat capacity
The amount of heat energy needed to change the temperature of a substance depends on:
– what the substance is;
– how much of it is being heated;
– what rise in temperature occurs.
• The heat energy needed to raise the temperature of an object by 1K is called the HEAT CAPACITY of the object.
• The SPECIFIC HEAT CAPACITY of a substance is the heat needed to raise the temperature of 1 kg of the substance by 1K.
What land features effect the climate
Mountain ranges can block the path of the wind blowing towards them, forcing the air to move quickly upwards to form almost permanent clouds, as water vapour in the air condenses quickly.
• Sandy soils reflect more energy from the sun than dark, fertile soils.
• Heavily vegetated areas absorb much more of the sun's radiation than bare land because plants use it to photosynthesise.
What are the requirements for a tropical cyclone
Warm Sea Surface Temperatures (above 27°C)
2. Strong Tropical Trade Winds (near the equator)
3. Moist Ocean Air
4. Low Air Pressure at Ocean Surface
How are cyclones formed
Warm ocean surface temperatures lead to large scale evaporation occurring in lower Troposphere.
This is primarily driven by huge quantities of heat energy being transferred into the water. Remember how much heat it takes to increase the temperature of water.
Water must be above 27°C
This warm, moist air over the ocean rises upward from near the surface. Because this air moves up and away from the surface, there is less air left near the surface.
Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below it.
Air from surrounding areas with higher air pressure pushes in to the low pressure area. This "new" air becomes warm and moist and rises, too.
Large amounts of heat energy still stored in the ocean surface increase the temperature of the new air.
As this warm, moist air continues to rise, the surrounding air swirls in to take its place.
As the warmed, moist air rises and condenses, the water in the air forms large-scale thunderstorm clouds (several of them).
The whole system of thunderstorms and wind grows, fed by the ocean's heat and water continuously evaporating from the surface and rising.
The growth of a tropical cyclone
If the cyclone continues to travel over warm water, the formation cycle will continue and the cyclone will grow in size.
• Because there is greater energy
being put into the system.
• Once a cyclone starts to travel over cooler water or land, this formation cycle is disrupted through rapid loss of heat energy, thus a reduction in mass evaporation.
• The cyclone will then lose strength.
Cyclone Yasi pathway, 2011
Why are cyclones more prevalent in tropical regions
More year-round sun radiation exposurewarmer sea temperature huge amount of energy into the system.
• Warmer sea temperatureMore surface evaporation.
• More evaporationWarm & Moist Air
• Greater chance of Large Low Pressure System Development.
• Earth is spinning quicker at the equatorstronger Coriolis effect on the winds coming into the system.
What is the coriollis effect
What is the greenhouse effect
The Earth's atmosphere acts like a giant invisible blanket that keeps temperatures on our planet's surface within a range that supports life.
• Within the atmosphere, greenhouse gases trap some of the heat energy leaving the Earth's surface to help maintain these warm temperatures.
• The maintenance of Earth's temperatures by these atmospheric gases is called the greenhouse effect.
What the problem with greenhouse gasses
Global temperatures have been increasing and are expected to continue to increase
at an accelerated rate. The rising temperature of Earth is known as global warming.
• This warming could threaten several of the processes/species living within the biosphere.
What's the enhanced greenhouse effect
GHGs are essential for life on Earth, however, human activities have seen certain GHGs rise to abnormal levels in the atmosphere.
• This causes a higher retention of heat energy.
• This is believed to be contributing to Global Warming.
How does the greenhouse effect work
The greenhouse effect occurs because greenhouse gases let
sunlight (shortwave radiation) pass through the atmosphere.
2. The Earth absorbs sunlight, warms then
reradiates heat (infrared or longwave radiation).
3. The outgoing longwave radiation is absorbed by greenhouse gases in the atmosphere. This heats the atmosphere which in turn re-radiates longwave radiation in all directions. Some of it makes its way back to the surface of the Earth.
What are implications of global warming
Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimetres) by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimetres).
• Hurricanes and other storms are likely to become stronger. Why do you think this is?
• Species that depend on one another may become out of sync. For example, plants
could bloom earlier than their pollinating insects become active.
• Floods and droughts will become more common.
• Tropical diseases will spread further away from the equatorial regions. (i.e. malaria carried by mosquitoes).
• Ecosystems will change—some species will move farther north or become more successful; others won’t be able to move and could become extinct.
• Wildlife research scientist Martyn Obbard has found that since the mid-1980s, with less ice on which to live and fish for food, polar bears have gotten considerably
skinnier. Polar bear biologist Ian Stirling has found a similar pattern in Hudson Bay. He fears that if sea ice disappears, the polar bears will as well
Where does the earth move the fastest and why
Equator- because the earths circumference is greatest meaning it travels the furtherest distance in one day
Why does the warm air head towards the poles
To equalise the temperature differences
How does the coriollis effect cause deserts
Most of the moisture if the air is left at the equator leaving drying air to create deserts
How are regular and reliable surface winds caused
The coriollis effect bends the air from the desert creating winds